swift234

Rename _isDebug and friends to _isDebugAssertConfiguration

Really we want those nullary functions be computed properties using enums.

  var _assertConfiguration : _AssertConfiguration {
    let assertConfig = Int32(Builtin.assert_configuration())
    if assertConfig == 0 {
      return .Debug
    }
    if assertConfig == 1 {
      return .Release
    }
    return .Fast
  }

  if _assertConfiguration == .Debug {
    _fatal_error_message("assertion failed", message, file, line)
  }

In my tests the enums were not optimized away. So for the short term leave
these functions as nullary functions.

Swift SVN r18211